Journal Article

Calcium Chelator and Channel Blockers Suppress the IAA-Induced Membrane Hyperpolarization without Inhibiting the Following Growth Promotion in Hypocotyl Sections of <i>Vigna unguiculata</i> under Xylem Perfusion

Koji Yuasa, Koji Takahashi and Kiyoshi Katou

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 39, issue 9, pages 978-986
Published in print September 1998 | ISSN: 0032-0781
Published online September 1998 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/oxfordjournals.pcp.a029462
Calcium Chelator and Channel Blockers Suppress the IAA-Induced Membrane Hyperpolarization without Inhibiting the Following Growth Promotion in Hypocotyl Sections of Vigna unguiculata under Xylem Perfusion

More Like This

Show all results sharing these subjects:

  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry

GO

Show Summary Details

Preview

The effects of the Ca2+ chelator EGTA and the Ca2+ channel blockers La3+, Gd3+, nifedipine, and verapamil on the IAA-induced early responses of hypocotyl sections of Vigna unguiculata were studied to assess the involvement of Ca2+ in the IAA-induced hyperpolarization followed by growth promotion using the xylem perfusion method. The IAA-induced hyperpolarization was distinctly inhibited by pretreatment with EGTA, La3+, and/or Gd3+ (5 mM each). EGTA inhibited by about 80–90% while La3+ and Gd3+ inhibited by about 60–75%. The sustained hyperpolarization after IAA application was also inhibited by these reagents. Nifedipine and verapamil (50 μM each) had little effect on the IAA-induced hyperpolarization and growth promotion. The inhibitory effects of EGTA, La3+ and Gd3+ on the membrane potentials were not due to changes in a passive component, but mainly to decreases in an elec-trogenic component. The effect of EGTA was reversible, while those of La3+ and Gd3+ were not. Present results suggest that the influx of Ca2+ through the plasma membrane might be required not only for the initiation of hyperpolarization by IAA but also for the following sustained hyperpolarization and may therefore play an essential role in the IAA-induced activation of the electrogenic proton pumps at the plasma membrane in Vigna hypocotyls. Inhibition of the hyperpolarization by EGTA, La3+, and Gd3+, however, did not involve inhibition of the promotion of growth by IAA. It seems that activation of the electrogenic proton pumps at the plasma membrane is not always the indispensable primary step of the IAA-induced promotion of elongation growth. Some alternative pathway of proton extrusion might take part.

Keywords: Ca2+; Elongation growth; IAA; Membrane hyperpolarization; Proton pump; Vigna unguiculata

Journal Article.  0 words. 

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

Full text: subscription required

How to subscribe Recommend to my Librarian

Users without a subscription are not able to see the full content. Please, subscribe or login to access all content.